The gist of this recent PRL paper by Salvatelli et al is the following: the tension between Planck's CMB data using a LambdaCDM model and many other data sources, such as Ho (Hubble constant at z=0) measurements by...you guessed it...the Hubble Space Telescope, can be resolved in a model in which dark matter decays into dark energy (but only when this interaction occurs after a redshift value of 0.9.) There has been a major problem reconciling the low value of Ho estimated by Planck's CMB data (Ho = 67.3 +/- 1.2) with the much higher value measured by the Hubble Space Telescope (Ho = 73.8 +/- 2.4 .)

However, when using a model in which dark matter can decay into dark energy, and when using RSD data on the fluctuations of matter density (as a function of the redshift, z), then the Planck estimate of the Hubble constant at z=0 becomes Ho = 68.0 +/- 2.3. This new model eases the tension between the Planck data and the Hubble Space Telescope measurement of Ho.

So, let's go into the details of the model:
(1) Dark matter can decay into dark energy (or vice versa is also possible in the model)
(2) The interaction between dark matter and dark energy is labeled 'q' in their model. When 'q' is negative, then this means that dark matter can decay in dark energy. When 'q' is positive, then this means that dark energy can decay in dark matter. And when 'q' is zero, then this is no interaction.
(3) The group has binned 'q' into a constant value over different periods of time.
Bin#1 is 2.5 < z < primordial epoch (in other words, from the Big Bang until ~5 billion years after the Big Bang)
Bin#2 is 0.9 < z < 2.5 (in other words, from ~5 billion years after the Big Bang to )
Bin#3 is 0.3 < z < 0.9
Bin#4 is 0.0 < z < 0.3 (i.e. most recent history)

Thursday, November 6, 2014

Not sure if you all have seen the recent article by Julian Barbour about an arrow of time arising from a purely gravitational system. If not, check out the following articles in Physics or Wired.
First off, the title of the articles contradict the substance of the articles.
Julian Barbour has shown that a system of 1000 objects interacting only via gravity can start dispersed, then clump together, and then disperse again. That's it. This is not exciting work. This was a similar problem to one that I was assigned in a freshman level computer programming class...just with ~100 objects rather than 1000 particles.

Second, Julian Barbour has shown that there is no arrow of time of for such systems, i.e. there is no way to tell the future from the past. (This is very different than let's say 'life', which only runs in one direction. You are born, you remember the past, and you eventually die.)

As such, Julian Barbour has re-proven something that has been known for quite awhile: In a system of particles that only interact via gravity, there is no arrow of time.

How can scientists and journalists mess this one up so badly? Thoughts?

Three Worlds, Three Mysteries

The Goal of this Blog

My goal is to communicate how life can expand and grow, both on this planet and on others. To grow, we need to obtain a large rate of return on investment from our power plants, so a main focus of this blog is on the economics of electricity generation and vehicle transportation.To summarize, the goal of life is to expand. Life requires mechanical or electro-chemical work to survive, and to grow, it requires a large, positive rate of return on work invested.

In other words, the purpose of a power plant is to make more power plants, and as quickly as possible.

After a series of posts on the topic of energy policy and economics, I thought that it'd be a good time to take a break and delve back i...

Good quotes

"The [engineer] should be equipped with knowledge of many branches of study and varied kinds of learning, for it is by his judgement that all work done by the other arts is put to test. This knowledge is the child of practice and theory."

Marcus Vitruvius Pollio, De Architectura, (~15 BC)

"The fact that the Standard Model of Physics has just enough complexity to be able to accommodate CP violation does not shed any light on the true nature of this phenomenon, and we feel the conclusion of J. Cronin's 1980 Nobel speech still stands: 'We must continue to seek the origin of the CP symmetry violation by all means at our disposal. [...] We are hopeful, then, that at some eposh, perhaps distant, this cryptic message from nature will be deciphered.' (Cronin, 1981) --Marco Sozzi, 2008, from the Coda of Discrete Symmetries and CP Violation

"Knowledge is power."

"Lastly, I would address one general admonition to all; that they consider what are the true ends of knowledge, and that they seek it not either for pleasure of the mind, or for contention, or for superiority to others, or for profit, or fame, or power, or any of these inferior things; but for the benefit and use of Life; and that they perfect and govern it in charity."— Francis Bacon

"Dare to be an optimist."

—Matt Ridley

"Stretch the range of human powers...Give us new metaphors with which to puzzle out our mysteries...Give us pride and higher aspirations...Turn our trash into treasure...Give us goals and meaning...Give us new tools with which we can connect...Validate us in our moments of confusion...Give us new rituals to make sense of our day...Give us new levels of reality...Give us your soul and bare your emotions...Give us new tools of understanding...Turn luxuries into everyday commodities...Warn us of our failings, of our conplacency, or our alternatives and of our dangers...Help us serve a purpose higher than ourselves."

—Howard Bloom, The Genius of the Beast

“Progress is possible only when people believe in the possibilities of growth and change. Races or tribes die out not just when they are conquered and suppressed, but when they accept their defeated condition, become despairing, and lose their excitement about the future.”—Norman Cousins

"If I had to choose a religion, the sun as the universal giver of life would be my god."— Napoleon Bonaparte

"Knowledge is of no value unless you put it into practice."— Anton Chekhov

"There is only one good, knowledge, and one evil, ignorance."

"Let no one ignorant of Mathematics enter [the Academy]."

— Plato/Socrates

"Perhaps the only goal on earth to which mankind is striving lies in this incessant process of attaining, in other words, in life itself..."

— Narrator of Dostoevsky's Notes from the Underground

"The physical holds no power over destiny."

—Norman Paperman

"Nature is not solely physical, even though everything in it must depend on the physical. Nature includes not only physical entities but complex material organizations, mathematical lawfulness, possibilities, life, need, behavior, intelligence, purpose, societies, minds, meanings, signs, and knowledge."

— Lawrence Cahoone, "The Orders of Nature"

"All men by nature desire knowledge."— Aristotle

"Worrying is praying for something that you don't want. So stop worrying!"

—Bhagavan Das

"Keep your head above the water and bet on the growth of your country."— Henry Flagler of Standard Oil

"Society will develop a new kind of servitude which covers the surface of society with a network of complicated rules, through which the most original minds & and the most energetic of characters cannot penetrate. It does not tyrannize, but it compresses, enervates, extinguishes & stupefies a people until each nation is reduced to nothing better than a flock of timid & industrious animals, of which the government is the shepherd."

"Socrates: 'Now, that which imparts truth to the known and the power of knowing to the knower is what I would have you term the idea of good, and this you will deem to be the cause of science, and of truth in so far as the latter becomes the subject of knowledge; beautiful too, as are both truth and knowledge, you will be right in esteeming this other nature as more beautiful than either; and, as in the previous instance, light and sight may be truly said to be like the sun, and yet not the sun, so in this other sphere, science and truth may be deemed to be like the good, but not the good; the good has a place of honor yet higher.'Glaucon: 'What a wonder of beauty that must be, which is the author of science and truth, and yet surpasses them in beauty; for you surely cannot mean to say that pleasure is the good?'

Socrates: 'God forbid, but I may ask you to consider the image in another point of view.'

Glaucon: 'In what point of view?'

Socrates: 'You would say, wouldn't you not, that the sun is not only the author of visibility in all visible things, but of generation and nourishment and growth, though he himself is not generation?'

Glaucon: 'Certainly.'

Socrates: 'In like manner, the good may be said to be not only the author of knowledge to all things known, but of their being and essence, and yet the good is not essence, but far exceeds essence in dignity and power.' "